feat(documents): expose thumbnailAspect + pageCount on Document entity

Adds ThumbnailAspect enum (PORTRAIT | LANDSCAPE) and maps the two
nullable columns from V53 as JPA fields so ThumbnailService can
populate them and the API can return them unchanged to the frontend.

Refs #305

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/src/main/java/org/raddatz/familienarchiv/model/Document.java

@@ -50,6 +50,13 @@ public class Document {
     @Column(name = "thumbnail_generated_at")
     private LocalDateTime thumbnailGeneratedAt;
 
+    @Enumerated(EnumType.STRING)
+    @Column(name = "thumbnail_aspect", length = 16)
+    private ThumbnailAspect thumbnailAspect;
+
+    @Column(name = "page_count")
+    private Integer pageCount;
+
     // Originaler Dateiname beim Upload (z.B. "Brief_Oma_1940.pdf")
     @Column(name = "original_filename", nullable = false)
     @Schema(requiredMode = Schema.RequiredMode.REQUIRED)

backend/src/main/java/org/raddatz/familienarchiv/model/ThumbnailAspect.java

@@ -0,0 +1,6 @@
+package org.raddatz.familienarchiv.model;
+
+public enum ThumbnailAspect {
+    PORTRAIT,
+    LANDSCAPE
+}

backend/src/test/java/org/raddatz/familienarchiv/repository/DocumentRepositoryTest.java

@@ -8,6 +8,7 @@ import org.raddatz.familienarchiv.model.DocumentAnnotation;
 import org.raddatz.familienarchiv.model.DocumentStatus;
 import org.raddatz.familienarchiv.model.Person;
 import org.raddatz.familienarchiv.model.Tag;
+import org.raddatz.familienarchiv.model.ThumbnailAspect;
 import org.raddatz.familienarchiv.model.TranscriptionBlock;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.jdbc.test.autoconfigure.AutoConfigureTestDatabase;
@@ -65,6 +66,40 @@ class DocumentRepositoryTest {
         assertThat(found.get().getStatus()).isEqualTo(DocumentStatus.PLACEHOLDER);
     }
 
+    // ─── thumbnailAspect + pageCount round-trip ───────────────────────────────
+
+    @Test
+    void save_persistsThumbnailAspectAndPageCount() {
+        Document document = Document.builder()
+                .title("Mit Aspekt")
+                .originalFilename("aspect.pdf")
+                .status(DocumentStatus.UPLOADED)
+                .thumbnailAspect(ThumbnailAspect.LANDSCAPE)
+                .pageCount(7)
+                .build();
+
+        Document saved = documentRepository.save(document);
+        Document found = documentRepository.findById(saved.getId()).orElseThrow();
+
+        assertThat(found.getThumbnailAspect()).isEqualTo(ThumbnailAspect.LANDSCAPE);
+        assertThat(found.getPageCount()).isEqualTo(7);
+    }
+
+    @Test
+    void save_thumbnailAspectAndPageCount_defaultToNull() {
+        Document document = Document.builder()
+                .title("Ohne Aspekt")
+                .originalFilename("no_aspect.pdf")
+                .status(DocumentStatus.PLACEHOLDER)
+                .build();
+
+        Document saved = documentRepository.save(document);
+        Document found = documentRepository.findById(saved.getId()).orElseThrow();
+
+        assertThat(found.getThumbnailAspect()).isNull();
+        assertThat(found.getPageCount()).isNull();
+    }
+
     // ─── findByStatus ─────────────────────────────────────────────────────────
 
     @Test